1. Field of the Invention
The present invention relates to a spectacle lens, which is designed and manufactured taking into consideration the distance between the center of rotation of the eye and a spectacle lens of an individual spectacles wearer, and a manufacturing method therefor.
2. Description of the Related Art
Despite the fact that spectacle lenses comprises single vision lenses and multifocal lenses (including progressive-power lenses) with different optical characteristics, they are generally designed on the basis of certain average utilization conditions. An example in which individual utilization conditions are taken into consideration is the method disclosed in Japanese Patent Application Laid-open No. 6-18823, in which there is proposed a progressive-power lens designed in consideration of individual utilization conditions, and there is disclosed the use of an aspheric surface, which is not accompanied by point symmetry axial symmetry in a prescription surface. The term xe2x80x9cutilization conditionsxe2x80x9d as used here refers to the distance between the back surface of a spectacle lens (the surface of the eye side) and the vertex of the cornea, the tilt of the frame, and so forth, and an attempt is made to optimize a prescription surface by using these data in lens design.
However, the technique disclosed in the above-mentioned publication has an object to optimize a progressive-power lens comprising a distance portion, a near portion, and an intermediate portion, and having a prescription surface for both far and near vision use, and in particular, takes into consideration the importance of utilization conditions in the case of a spectacle lens, like a progressive-power lens, having a prescription, which supplements the accommodative power in near vision for presbyopia. This is because a progressive-power lens requires particularly accurate adjustment of s determining the conditions of a corrective prescription, is deemed particularly necessary. Therefore, the disclosure in the publication only emphasizes the accurateness of a near use prescription, and does not address overall wearing conditions for lenses such as spherical design lenses, aspherical single vision lenses, and bifocal lenses.
The present invention was devised based on the above-mentioned circumstances, and has as an object to provide a spectacle lens and a manufacturing method thereof, having a prescription surface which has been further optimized by reviewing the wearing conditions for all spectacle lenses, which was not paid much attention to in the past, and by taking into consideration individual wearing conditions.
As a means for solving the above-mentioned problems, a first invention is a spectacle lens characterized in that a spectacle lens is designed by using a value determined by either measuring or specifying for an individual spectacles wearer the value of the distance VR from a reference point on the back surface of a spectacle lens to the center of rotation of the eye, which adds together the value of the distance VC from a reference point of the back surface of a spectacle lens to the vertex of the cornea of the eye of the spectacles wearer at spectacle lenses wearing time, which is one of the required data in spectacle lens design, and the distance CR from the above-mentioned vertex of the cornea to the center of rotation of the eye, and manufacturing a spectacle lens based on this design specification.
A second invention is a spectacle lens related to the first invention, characterized in that the value of the distance CR from the above-mentioned vertex of the cornea to the center of rotation of the eye utilizes a value obtained based on measurement data obtained by measuring the axial length of the eye CO of a spectacles wearer.
A third invention is a spectacle lens related to either the first invention or the second invention, characterized in that the above-mentioned center of rotation of the eye is determined for distance vision, near vision, specified distance vision, and combination thereof, respectively, and is either selected and used on the basis of lens optical characteristics, or is used for appropriate viewing areas of a spectacle lens, respectively.
A fourth invention is a spectacle lens characterized in that it is processed by obtaining an optimized lens form based on an optical model of wearing conditions simulated in accordance with design and/or processing condition data information selected as needed from among information comprising a prescription value, which comprises spectacle lens information, spectacle frame information, and data related to the individual VR value of a spectacles wearer, layout information, and process specification information.
A fifth invention is a spectacle lens related to the fourth invention, characterized in that an amount of inset for near vision is determined based on the above-mentioned VR value.
A sixth invention is a spectacle lens related to the fourth invention, characterized in that the base curve of a convex surface is determined based on the above-mentioned VR value.
A seventh invention is a spectacle lens related to the fourth invention, characterized in that power error correction for a pre-set reference prescription surface is performed based on the above-mentioned VR value.
An eighth invention is a spectacle lens manufacturing method, wherein a terminal apparatus, which is installed at a spectacle lens ordering party, and an information processing system, which is installed at a spectacle lens processing party, and is connected by a telecommunications line to the above-mentioned terminal apparatus are provided for designing and manufacturing a spectacle lens based on information sent to the above-mentioned information processing system via the above-mentioned ordering party terminal apparatus; this spectacle lens manufacturing method comprising the steps of:
sending to the above-mentioned information processing system via the above-mentioned terminal apparatus design and/or processing condition data information selected as needed from among information comprising a prescription value, which comprises spectacle lens information, spectacle frame information, and data related to the VR value of each spectacles wearer, layout information, and process specification information; and
obtaining an optimized lens form based on an optical model of wearing conditions simulated by the above-mentioned information processing system, determining processing conditions, and manufacturing a spectacle lens.
A ninth invention is a spectacle lens manufacturing method, wherein, a terminal apparatus, which is installed at a spectacle lens ordering party, and an information processing system, which is installed at a spectacle lens processing party, and is connected by a telecommunications line to the above-mentioned terminal apparatus are provided for designing and manufacturing a spectacle lens based on information sent to the above-mentioned information processing system via the above-mentioned ordering party terminal apparatus, this spectacle lens manufacturing method comprising the steps of:
sending to the above-mentioned information processing system via the above-mentioned terminal apparatus design and/or processing condition data information selected as needed from among information comprising a prescription value, which comprises spectacle lens information, spectacle frame information, and data related to the VR value of each spectacles wearer, layout information, and process specification information:
determining an optimized lens form based on an optical model of wearing conditions simulated by the above-mentioned information processing system;
also determining a standardized lens form by the above-mentioned information processing system using a standardized VR value in place of said VR value obtained for each spectacles wearer, while using other design and/or processing condition data sent via the above-mentioned terminal,
comparing the optical characteristics of the above-mentioned optimized lens form against the optical characteristics of the above-mentioned standardized lens form, and based on the results of the comparison thereof, selecting either one of the above-mentioned lens forms, determining processing conditions of this selected lens form, and manufacturing a spectacle lens.
A tenth invention is a spectacle lens manufacturing method wherein, a terminal apparatus, which is installed at a spectacle lens ordering party, and an information processing system, which is installed at a spectacle lens processing party, and is connected by a telecommunications line to the above-mentioned terminal apparatus are provided for designing and manufacturing a spectacle lens based on information sent to the above-mentioned information processing system via the above-mentioned ordering party terminal apparatus, this spectacle lens manufacturing method comprising the steps of:
inputting via the above-mentioned terminal apparatus design and/or processing condition data information selected as needed from among information comprising a prescription value, which comprises spectacle lens information, spectacle frame information, and data related to the VR value of a spectacles wearer, layout information, and process specification information; and
obtaining an optimized lens form based on an optical model of wearing conditions simulated on the basis of the inputted information thereof, determining processing conditions, and manufacturing a spectacle lens.
The present invention makes it possible to achieve a higher performance spectacle lens by designing a spectacle lens using a value determined for each individual spectacles wearer, as a value of distance VR from a reference point on the back surface of a spectacle lens to the center of rotation of the eye when the spectacle lenses is worn, which is one of the necessary data in the lens design, and manufacturing the lens based on the design specifications thus established.
Conventional thinking holds that it is sufficient to use a standard value as a VR value, and that the effects that individual differences of a VR value have on lens performance are practically negligible. That is, as indicated in the above-mentioned Japanese Patent Application Laid-open No. H6-018823, with the prior art, a spectacle lens has been designed and manufactured using a standard value as the distance from the center of rotation of the eye to the vertex of the cornea. However, the fact is that although a VR value determined on the basis of this standard distance is known to be a value that differs from individual to individual, it has not been well known or accurately verified what effect this difference has on optical effects, that is, on design of the spectacle lenses. There are a variety of design methods for an optical surface of a spectacle lens, and the main concern was optimization of design thereof, while it was out of consideration to verify or simulate the effect of a VR value for each design. Further, quite naturally, sufficient study has not been done on how this value should be fed back to the design and manufacture processes.
The inventors investigated the differences in VR values between individuals, and conducted research on this subject using a simulation method such as the ray tracing method recently developed. They finally found out that differences in VR values between individuals are unexpectedly large, and the effects of these differences on lens performance are also greater than expected. Based on the results of this research, lenses of common basic specifications were actually designed and manufactured in two types, that is, lenses for which differences in VR values between individuals were taken into consideration, and those for which they were not, and their performance were compared. The results the inventors obtained greatly exceeded their expectations.
That is, it was ascertained that there was large difference in optical performance of a spectacle lens in a case where a spectacle lens designed and manufactured based on a standard VR value was used for an individual having a different VR value from the standard VR value, and such difference reached an amount requiring correction. Specifically, there are effects related to optical layout related to aberration of a single-focus lens, the positioning of the segment height when the refracting power at the vertex of the distance portion in bifocal lenses is different between the right and left lenses, an amount of inset of the near portion in progressive-power lenses, height of the near portion and so on.
Here, the value of the sum of a value of the distance VC from a reference point on the back surface of a spectacle lens to the vertex of the cornea of the eye of the spectacles wearer as found when spectacle lenses are being worn by the wearer, and a value of the distance CR from this vertex of the cornea to the center of rotation of the eye can be used as the VR value.
For the present invention, the most important factor is the CR value, and because a CR value will differ physiologically from individual to individual, it is desirable that a CR value be accurately calculated by measurement. However, according to circumstances, individual CR values will not be necessary for all the cases. For example, it is also possible that CR values are classified into 2 to 5 groups, a value representing the respective groups is set, and this value is used as a CR value for the group. In the present invention, values as designated by an ordering side, including measured values in the broad sense are used as the CR values in lens design.
As a method for measuring a CR value, for example, it is possible to use the eye rotation point measuring apparatus proposed by G. A. Fry and W. W. Hill and described in an article titled xe2x80x9cTHE CENTER OF ROTATION OF THE EYExe2x80x9d in the AMERICAN JOURNAL OF OPTOMETRY and ARCHIVES of AMERICAN ACADEMY OF OPTOMETRY (vol. 39, published November 1962). Further, there is also a method, by which a CR value is found by computing from the point of intersection of lines of sight of different directions.
Further, as a simple and practical method, there is a method of utilizing a widely used apparatus for measuring the axial length of the eye. That is, it is a method, which measures the axial length of the eye, wherefrom finds the central point of rotation of the eye by calculation. For example, in this method, general statistical data of the relative position of the rotating point of the eye to a previously measured axial length are used. For example, if it is supposed that, as average data, the axial length of the eye is 24 millimeters, and the distance from the vertex of the cornea to the central point of rotation (CR) is 13 millimeters, 13/24=0.54 constitutes the utilization ratio. Therefore, in the case of a person, for whom the axial length of the eye is detected as 27 millimeters, using this relative position coefficient 0.54, it is supposed that the value of this person""s CR is 27 millimetersxc3x970.54=14.6 millimeters. In addition thereto, various methods can be used to find the correlation between the point of rotation of the eye and the axial length of the eye for establishing the point of rotation of the eye.
There are various apparatuses for measuring the axial length of the eye, including, for example, ultrasonic sound measuring apparatuses and sight line direction detecting apparatus. Further, the location of the central point of rotation of the eye is not a fixed point in the eye, but rather is believed to change slightly in accordance with the direction or distance one is trying to view, as when viewing at a distance, and when viewing up close. Therefore, preferably, it is desirable to carry out processing on data differently according to the properties of the lens being designed, before using same in a design. For example, in the case of a progressive-power lens, different values of the location of central point of rotation as found in distance vision and in near vision are used respectively, for the distance vision region and the near vision region; in the case of a single vision lens for distance vision, a value of the location of central point of rotation as found in distance vision is used; and in the case of single vision lens for presbyopia, a value of the location of central point of rotation as found in near vision is used. Further, it is also possible to treat measurement data from one direction as basic data, apply corrective values thereto, and use this measurement data in various ways.
Further, there is no special measuring apparatus for determining a VC value like there is for a CR value, but it is important to accurately determine a VC value. But this value differs from a CR value, and is not a purely physiological value, and since there is also a correlation between a VC value and the wearing condition of a frame, this value is adjusted by the side that transmits a prescription value (an optometrist, optician, or the like). Since there are also cases in which a VC value can be adjusted to a certain prescribed value (for example, a value determined by an optician), in the present invention, VC values are treated, in the broad sense, as designated values.
In this manner, according to the present invention, spectacle lens design is performed for the right and left eyes of each individual by using a VC value for the distance from a reference point on the back surface of a spectacle lens to the vertex of the cornea of the eye of a spectacles wearer, and a CR value for the distance from the vertex of the cornea to the center of rotation of the eye, but it is also important to compare a spectacle lens designed according to the present invention against a standard spectacle lens designed and manufactured by an existing design technique, and to give comparative data as to how different they are.
That is, because lenses, which were designed as spectacle lenses using a VC value and a CR value of the right and left eyes of each individual, respectively, are individually designed products that are manufactured one product at a time, manufacturing costs are higher than for a standardized product (standard product) that is manufactured in volume.
However, there are cases when even lenses, which were designed as spectacle lenses using a VC value and a CR value of the right and left eyes of each individual, respectively, become identical to a standard product, and there are cases when even if there is a difference, it is only a slight difference. In such cases, it will be disadvantageous for the end user to select and purchase a relatively expensive product that is manufactured one product at a time. Naturally, it is clear that the performance of the spectacle lenses by a design based on individual by individual information would not differ greatly even when compared to a standard product. In other words, it is believed the user would feel like the newly prepared spectacles do not differ much compared to the spectacles he had used up until now, and would feel displeased at having selected and purchased a relatively expensive product.
Thus, it is necessary to clarify the difference in optical characteristics (astigmatism, average power, power error, and so forth) between a standard product and a spectacle lens by a design based on individual by individual information when trying to make a selection prior to ordering a spectacle lens.
Thus, when ordering information, such as a prescription value, which comprises spectacle lens information, spectacle frame information, and data related to a VR value of each spectacles wearer from a spectacles store, layout information, and process specification information is sent to the information processing system of the spectacles processor side from the terminal apparatus of the spectacles store side, it is necessary to compute in the information processing system of the processor side the difference between a standardized product and spectacle lenses by a design based on individual by individual information, which was either ordered, or inquired about, to send a reply to the terminal apparatus of the spectacles store side, and to display optical characteristic information, such as an astigmatism distribution chart, and an average power distribution chart.
By providing comparative information in this manner, it becomes possible to cancel the selection of an individually designed product and purchase a standardized product when there is not much difference between an individually designed product and a standardized product.